Q16-70E - Organic Chemistry (Mcmurry)

Question

Propose a mechanism to account for the reaction of benzene with 2,2,5,5 tetramethyltetrahydrofuran.

Step-by-Step Solution

Answer

Mechanism followed as:

a.

b.

c.

d.

Step 1: Reaction of benzene with 2,2,5,5-tetramethyltetrahydrofuran.

1. Protonation of the cyclic ether occur which lead to the opening of the ring and the formation of carbocation takes place which is undergo Friedal craft alkylation as shown:

Reaction with 2,2,5,5-tetramethyltetrahydrofuran

Step 2: Friedel craft alkylation

Benzene act as a nucleophile and attacks the carbocation and followed by the base which abstract the proton formation of the alcoholic product occurs follow:

Friedal craft alkylation

Step 3: Protonation of alcohol

The hydroxyl proton of the alcohol is protonated and followed by the hydrolysis that the loss of water molecule leads to the generation of the secondary carbocation as shown below:

Protonation of alcohol

Step 4: Internal alkylation

As the second carbocation is undergo internal alkylation that the shift of the alkyl group leads to the formation of the desired product occur:

Internal Alkylation